Time delay glow switch



TIME DELAY GLOW SWITCH Filed Cot. 25, 1941.

BY ,Mmmm

ATTO R N EY Patented June l5, 1943 x 2,321,910 TIME DELAY GLow SWITCHRobert F. Hays, Jr., East Orange, N. J., assignor to WestinghouseElectric &

Manufacturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application october- 23, 1941, serial No. 416,172 l 7Claims.

The present'invention relates to what is known to the art as a glowrelay device now commercially employed for the starting of uorescentlamps ,and constitutes an improvement over such a device as shown'ln myprior Patent 2,228,210, issued January '1, 194i, and assigned to thesame assignee as the present invention.

Certain standards have now been established for devices of thischaracter, and while prior structures under some conditions comply withthese standards, it has not invariably followed that they aresatisfactory under all operating conditions. There are severaldesiderata for devices of this type which must be fulfilled to lnsuresatisi'actory operation under all conditions. For example, the glowrelay must operate very rapidly so as to complete a heating circuit tothe therrnionic electrodes of the fluorescent lamp, and this heatingcircuit must be maintained closed for a sufdcient period of time toallow the 'electrodes to be heatedto maximum electronemittingtemperature prior to further operation ci the glow relay to cause a highvoltage surge to be applied across the electrodes, otherwise such highvoltage will result in a deterioration of the electrodes with asubstantial shortening in the life of the lamp.

Consequently, during the iirst two phases of operation of the' glowrelay two diametrically opposite requirements are necessary; first,rapidity of operation and, secondly, a slight time delayof not iess thanapproximately 1.35 seconds. Moreover, since both uorescent lamps andglow relays are used on both leading and lagging power factor circuits,slightly different conditions en lst which heretofore have resulted inthe operation of the glow relay being somewhat slower when employed in aleading power factor circuit than in the case of a lagging power factorcircuit.

. In addition, it has not been feasible heretofore to employ getters inconjunction with glow relay devices to remove occluded gases whichotherwise contaminate the gaseous filling because of the fact that theycause the breakdown voltage of the device to be too low for practicaloperation for the intended purpose of starting a fluorescent lamp.

llt is acordingly an object of the present invention to provide a glowrelay device which initially operates very rapidly and with apredetermined time delay during further stages of its operation.

Another object of the present invention is the provision of a glow relaydevice which operates with a predetermined time delay to enable thethermionic electrodes of a fluorescent lamp to be (Cl. Z50-27.5)

Another object of the present invention is the provision (of a glowrelay devicewhlch is ei' iiciently operable either with a leading orlagging power factor circuit for the starting of a fluorescent lamp.

A further object of the present invention is the provision oie. glowrelay device for'the starting of fluorescent lamps' wherein a getter isemployed for removing impurities in the gas without deleteriouslyaffecting the breakdown voltage of the device.

Still further objects of the present invention will become obvious tothose skilled in the art by reference to the accompanying drawing where-Fig. l is an elevational view partly insection and on .an enlarged scaleof a glow relay device constructed in accordance with the presentinvention.

Fig. 2 is a sectional View taken on the line lli-II of Fig. l.

Fig. 3 is a plan view partly in cross section of a portion of one of theelectrodes and taken on the line lli-dll of Fig. l.

Fig. i is a view similar to Fig. 3, but showing a slight modificationwhich one of the electrodes may taire. ,l

Fig. 5 is a schematic diagram of a leading power factor circuit forenergizing a fluorescent lamp in which the glow relay device of thepresent invention may be employed.

Fig. 6 is a schematic diagram similar to Fig. 5 but showing a laggingpower factor circuitfor energizing'the lamp and employing the glow relayof the present invention.

Referring now to the drawing in detail, the device as shown in Fig. icomprises an envelope t, which may be of a vitreous material such asglass or the like, and after evacuation through an ex-l haust tip t isfilled with an ionizable medium such as argon, neon, helium, or amixture thereof. A pair of leading-in and supporting conductors l and dare sealed into a press portion 9 of the enheated to a sulicently hightemperature with rey sulting copious fiow of electrons before theapplication of a high starting voltage to the lamp electrodes, thuseliminating deleterious results to the latter which would otherwiseensue.

velope and extend a slight distance interiorly of the enveloped. Anelectrode in the form of a U-shaped bimetallic element itl has one ofits ends welded or otherwise afiixed to the leadingin conductor t withthe free end thereof suspended in juxtaposition to the extending end oithe remaining leading-in conductor 1.

The structure thus far described is identical to that shown and claimedin my above noted patent. In order to impart a predetermined time delayduring actual closure of a circuit by en' being that it (be of suchmaterial that it heats quickly and its surface area not be too great soas to sacrifice the high transient voltage resulting uponseparation ofthe electrodes as disclosed in my above mentioned patent.

Ihe advantage of such construction resides in the fact that upon theapplication of a voltage sumcient .to break down the device, a glowdischarge results between the electrodes III and I2, due to thebimetallic electrode III emitting electrons because it is a metal of lowwork function or it may be provided with an electron-emitting coating.if desired. 'I'he ensuing glow discharge heats the tungsten filament I2,which is of comparatively small surface area, to a temperaturesuiiiciently high that it in turn begins to emit electrons by thermionicemission and the glow discharge is converted 'into an arc discharge, thelatter theny raising the temperature of the tungsten electrode I2substantially to white heat. 'I'he bimetallicelectrode Il is likewiseheated by both the glow discharge and the subsequent arc discharge anddefiects'so that a substantial portion of its surface area contacts acomparable portion oi' the contiguous surface area of the lamentaryelectrode I2, as shown by the dotted lines in Fig. 1, thusshort-circuiting the electrodes and extinguishing the discharge.

However, since the iilamentary electrode I2 is substantially at whiteheat and -is disposed in close proximity to the bimetallic electrodeIII, this heat is transmitted to the bimetallic electrode IU byradiation and by conduction through the contacting surface areas, thuscausing a predetermined time delay before the bimetallic electrode coolssufnciently to separate from the lamentary electrode and return to itsnoi-mal position. This time delay is necessary so that when the glowrelay, device is employed in'a circuit such as shown in Fig. 5 forstarting a fluorescent lamp, the lamp electrodes It and'II are heated toa -suiilciently high electron-emitting temperature before the high-voltage surge induced by the inductance IlA is impressed across theelectrodes I6 and I1 at the instant of separation of the glow relayelectrodes Il and I2'upon cooling of the blmetallic electrode Il.

This resulting time delay is of further advantage particularly when aglow relay device of the present invention is employed for starting ailuorescent lamp when operated on a leading power factor circuit, suchas shown in Fig. 5, which includes a series condenser I5. Ashereinbefore mentioned, previous types of glow switches have operatedfairly satisfactorily on lagging power factor 'circuits such as shown inFig. 6 wherein the lamps are of the lower wattage type. However, whenoperated on leading power factor circuits, which necessarily include a.condenser in series with the inductance, they have closed verly slowly.,In order to produce a high transient voltage at the instant ofseparation of the electrodes, oneelectrode must be small, as describedand claimed in my above noted patent, which results in the glow switchoperating or functioning as a rectifier, thus charging the seriescondenser with D. C.,voltage. 'Ihis D. C. voltage subtracts from the A.C. supply voltage during the half cycle that the bimetallic electrodefunctions as cathode so that little heat is produced and the electrodesclose very slowly. On the other half cycle when the small electrode iscathode, the D. C. voltage on the series condenser adds to the A. C.supply voltage and produces a great amount of heat at the smallelectrode.

Accordingly, the small electrode functions as 'cathode muy 50% of thetime, and the rapidity of operationI of the glow relay is dependent uponthe particular half cycle of the voltage impressed across the electrodesVat the instant of starting. In the structure of the glow switch of thepresent I invention' wherein the electrode I2 comprises a small tungstencoil, the sameaction takes place for an instant. The abnormally greatamount of heat applied to the lamentary electrode I2 causes it to becomea good thermionic emitter, so that its emission exceeds that of thebimetal, and the condenser I9 charges up in the opposite direction.

Thus,'even on the half cycle when the bimetallic electrode I0 ismomentarily functioning as cathode, the voltage on the condenser I9 addsto the A. C. supply voltageA so that the bimetallic electrode I0 heatsvery rapidly and the electrodes contact each other very quickly. Theactual result is that the glow relay of the present invention, incontradistinction to previous types,

f' operates more quickly on a leading power factor circuit than on alagging power factor circuit, although its rapidity of operation even ona lagging power factor circuit is well within the standards now fixed bylamp manufacturers.

In addition to the glow relay of the present invention providing apredetermined time delay during one phase of its operation, theconstruction thereof also makes it possible to employ getters Withoutaffecting the break-down voltage of the device. Inasmuch as thefilamentary tungsten electrode I2 is substantially at white heat due tothe ensuing arc discharge, the hot tunsten reacts with some impuritiesin the filling gas and thereby serves as a getter. The tungsten coilalso makes possible the use of more eiiicient getters, such as zirconiumor tantalum, which require a. high temperature to produce gettering.Asmall sliver or slug 20 of such materials may be inserted in the coilin the manner shown in Fig. 4, or the materials may be applied to thetungsten coil in the form of paint, as shown at 22 in Fig. 3, whicheliminates the necessity ofA flashing the getter with high frequencywhile on the exhaust machine.

It should thus become obvious to those skilled in the art that a glowrelay device is herein provided wherein the bimetallic electrode isheated very rapidly so that the relay very quickly performs its initialoperating step. Also, due to the present construction, a predeterminedtime delay is provided which maintains the electrodes jin contact witheach other, thus enabling the filamentaryelectrodes of a discharge lampto be heated to a sufiiciently high temperature that a copious ow ofelectrons ensues prior to separation of' the electrodes upon cooling ofthe bimetallic element. This accordingly eliminates the application of ahigh voltage surge to the lamp electrodes prior to their being heated tosubstantially maximum electron-emitting ternperature, which wouldotherwise cause sputtering of the electrodes and thereby materiallylessening the useful life of the lamp.

Although one specific embodiment of the present invention has been shownand described, it is to be understood that other modifications of thesame may be made without departing from the spirit and scope of theappended claims.

I claim:

1. A gaseous electric device comprising an envelope provided with anionizable medum therein and a rpair of electrodes, one of which is athermo-expansive electrode adapted to emit electrons to cause a glowdischarge between said electrodes thereby heating the same withattendant movement of said thermo-expansive electrode into contact withthe other of said electrodes to short-circuit the same and extinguishsaid discharge, and said thermo-expansive electrode being movable awayfrom said other electrode upon cooling, and means independent of saidelectrodes for heating said thermo-expansive electrode for a shortperiod of time following engagement of said electrodes to impart aslight time delay in the separation thereof upon cooling of saidthermo-expansive electrode.

2. A gaseous electric device comprising an envelope provided with anionizable medium therein and a pair ofrelectrodes, one of which is athermo-expansive electrode adapted to emit electrons to cause a glowdischarge between said electrodes thereby heating the same withattendant movement of said thermo-expansive electrode into contact withthe other of said electrodes to short-circuit the same and extinguishsaid discharge, and said thermo-expansive electrode being movable awayfrom said other electrode upon cooling, and means associated with the,other of said electrodes for transmitting heat to said thermo-expansiveelectrode for a short period of time following their engagement andafter extinguishment of said discharge to impart trode being movableaway from said other elec-y trode upon cooling, and said other electrodebeing of a metal which is heated by the discharge to a highertemperature than said thermo-expansive electrode and operable totransmit its heat to said thermo-expansive electrode afterextinguishment of said discharge to cause a slight time delay in theseparation of said electrodes upon cooling of said thermo-expansiveelectrode.

4. A gaseous electric device comprising an envelope provided with anionizable medium therein and a pair of electrodes, one of which is athermo-expansive electrode adapted to emit electrons to cause a glowdischarge between said electrodes thereby heating the same withattendant movement of said thermo-expansive electrode into contact withthe other of said electrodes to short-circuit the same and extinguishsaid discharge, and said thermo-expansive electrode be# ing movable awayfrom said other electrode upon cooling, and said other electrodecomprising a refractory metal Winding and heated bythe discharge to ahigher temperature than saidthermoexpansive electrode and operable totransmit its heat to said thermo-expansive electrode afterextinguishment of said discharge to cause a slight time delay in theseparation of said electrodes upon cooling of said thermo-expansiveelectrode.

5. A gaseous electric device comprising an envelope provided with anionizable medium therein and a pair of electrodes, one of which is athermo-expansive electrode adapted to emit electrons to cause a glowdischarge between said electrodes thereby heating the same withattendant movement of said thermo-expansive electrode and contact of anappreciable surface area thereof with a comparable surface area of theother of said electrodes to short-circuit the same and extinguish saiddischarge, and said thermo-expansive electrode being movable away fromsaid other electrode upon cooling, and said other electrode having asurface area substantially less than said thermo-expansive electrode andheated by the discharge to a higher temperature than the latter andoperable to transmit its heat through the contacting surfaces ofappreciable area to said thermo-expansive electrode after extinguishmentof said discharge to cause a slight time delay in the separation of saidelectrodes upon cooling of said thermo-expansive electrode.

6. A gaseous electric device comprising an envelope provided with anionizable medium therein and a pair of electrodes, one of which is athermo-expansive electrode adapted to emit electrons to cause a glowdischarge between said electrodes thereby heating the same withattendant movement of said thermo-expansive electrode into contact withan appreciable surface area of the other of said electrodes toshort-circuit the same and extinguish said discharge, and saidthermo-expansive electrode being movable away from said other electrodeupon cooling, and said other electrode comprising a refractory metalhelix having a surface area substantially less than that of saidthermo-expansive electrode and heated by the discharge to a highertemperature than said thermo-expansive electrode, and operable totransmit its heat through its contacting surface area to saidthermo-expansive electrode after extinguishment of said discharge tocause a slight time delay in the separation of said electrodes uponcooling of said thermoexpansive electrode.

7. A gaseous electric device comprising an envelope provided with anionizable medium therein and a pair of electrodes, one of which is athermo-expansive electrode adapted to emit electrons to cause a glowdischarge between said electrodes thereby heating the same withattendant movement of said thermo-expansive electrode and contact of anappreciable surface area thereof with a comparable surface area of theother of said electrodes to short-circuit the same and extinguish saiddischarge, and said therm( expansive electrode being movable away fromsaid other electrode upon cooling, said other electrode having a surfacearea substantially less than said thermo-expansive electrode and heatedby the discharge to ahigher temperature than the latter and operable totransmit its heat through the contacting surfaces of appreciable area,to said thermo-expansive electrode after extinguishment of saiddischarge to cause a slight time delay in the separation of saidelectrodes upon cooling of said thermo-expansive electrode. and meansassociated with said electrodes within said envelope and operable as agetter for absorbing impurities in said lling gas. Y

ROBERT F. HAYS, JR.

